1. Field of the Invention
The present invention concerns a separator for separating two or more materials, of which one consists of a particulate, fluidisable powder material, such as aluminium oxide, Al.sub.2 O.sub.3 (hereinafter called oxide), from a material which cannot be fluidised, such as, for example, nails, tools, coke, pieces of wood, lumps of oxide.
2. Description of Prior Art
Oxide is used as the main component when producing aluminium in a Hall-Heroult electrolysis process and is forwarded by bulk carrier ship from the supplier to the aluminium works. At works which produce anodes and/or cathodes, the oxide is unloaded in most cases using the same equipment as is used for unloading coke/anthracite. Undesired material components in the oxide can be transported and added during the various transport phases from an oxide works to the electrolysis cells. Furthermore, the oxide may become lumpy, which is not desirable from an operational point of view.
If undesired, non-fluidisable materials are introduced into the electrolysis cells' bath, this may cause operating problems in the electrolysis cells and a significant reduction in quality of the aluminium product.
In order to avoid the above-mentioned problems, a separator is usually inserted ahead of the electrolysis cells so that only fluidisable, i.e. purified, oxide is fed into the cells.
A number of procedures are known for separating oxide. Most of them have too little capacity on the one hand and the separating effect is too low on the other. Norwegian patent no. 167263 describes a device for separating fluidisable material from non-fluidisable material. An eddy layer apparatus and screens are used in a chamber which is placed on spiral springs. Furthermore, the chamber is vibrated mechanically and periodically to avoid the chamber becoming overfilled, as well as to increase the capacity. A disadvantage of this procedure is the wear caused to the chamber, the sleeves and the screens during vibration and eddies; in the long term this can be expensive on account of maintenance, repairs and production disturbances. Moreover, it is generally known that productivity is low with mechanical vibration screening.